Airtel — postpaid bill transaction, extra bill amount still not refunded.

Address:

Pune, Maharashtra, 411061

Hello,
I am vardhaman aitawade. I have airtel postpaid number [protected] (Maharashtra).
On 2nd december 2017 i converted it postpaid to prepaid with paid all the outstanding ammount by using netbanking at devidas airtel pimple saudagar pune.
My outstanding amount is 640/- rs but same time my account debited two times. (640 + 640 = 1240 rs)
I can complaint immediately to airtel, they said extra amount will sending you at billing address by cheque, within 45 days. Today is almost 60 days completed, but still i can't get cheque. So i called airtel customer care, people are not responding properly, and again they said wait more 90 days.
Kindly requesting you please resolve this problem and refund my money as soon as possible.
Please find below mentioned transaction details.

1. [protected]/citrus airtel
2. [protected]/citrus airtel